2007 U.S.-Belgium income tax treaty

https://www.irs.gov/pub/irs-trty/belgiumtt06.pdf

1. If an individual qualifies to be considered a resident of both the United States and Belgium, what criteria does the treaty use to "break the tie" and determine the country of residence?
2. How does the treaty define a permanent establishment for determining nexus?
3. Identify two other provisions in the treaty that you found interesting, and why you found them interesting.